Process for producing shaped steel parts

Abstract

A process for producing a shaped part of a pre-form of hardenable and heat formable steel sheet, by means of heat treatment with cold deforming tools, in which by the heat forming a hardened component is produced, which exhibits a martensitic and/or banitic microstructure, wherein the hardened component is tempered subsequent to heat forming so that a shaped part is formed which exhibits, at least in areas, a higher yield strength and a pronounced break limit compared to the hardened component.

1 . A process for producing a shaped part from a pre-form of hardenable and heat deformable steel sheet metal, by means of heat forming with cold deforming tools, in which by hot forming a hardened component is produced, exhibiting martensitic and/or banitic microstructure, wherein the hardened component is tempered subsequent to hot forming, so that a shaped component is produced, which in comparison to the hardened component condition, exhibits at least in areas a higher yield strength and/or pronounced yield strength.  
   
   
       2 . The process according to  claim 1 , wherein temperature and duration of tempering are so selected, that the yield strength is increased by at least 20%.  
   
   
       3 . A process for producing a shaped part from a pre-form of hardenable and hot deformable steel sheet metal, including the steps: 
 a) heating the preform to an austenitising temperature;    b) press hardenening in a cold tool as a result of which, by quencing, at least partially a martensitic and/or banitic microstructure is produced,    c) wherein an annealing of the shaped pre-form at temperatures below 400° C. with formation of a shaped part with increased yield strength and/or break elongation occurs in comparison to the hardened component.    
   
   
       4 . The process according to  claim 1 , wherein the pre-form is a chrome-molybdenum steel.  
   
   
       5 . The process according to  claim 3 , wherein the chrome-molybdenum steel is 25CrMo4, 34CrMo4 or 42CrMo4.  
   
   
       6 . The process according to  claim 1 , wherein the pre-form is a boron alloyed case hardened and heat treated steel.  
   
   
       7 . The process according to  claim 7 , wherein the boron alloyed case hardened and heat treated steel is 17MnB3, 22MnB5 or 27MnCr5-2.  
   
   
       8 . The process according to  claim 1 , wherein the pre-form is a flat plate, a cold deformed steel pre-form or cut or trend pre-form.  
   
   
       9 . The process according to  claim 1 , wherein the annealing occurs at a temperature in the range of 250 to 400° C.  
   
   
       10 . The process according to  claim 1 , wherein the annealing occurs at a temperature of from 300 to 330° C.  
   
   
       11 . The process according to  claim 1 , wherein the hardened pre-form is cut to its final contour prior to or subsequent to step c).  
   
   
       12 . The process according to  claim 1 , wherein the surface of the hardened shaped part is cleansed prior to annealing, in particular, by a powder blasting process.  
   
   
       13 . The process according to  claim 1 , wherein during annealing in step c) at the same time also a surface treatment for formation of a defined corrosion protection and/or friction resistance for the shaped part occurs.  
   
   
       14 . The process according to  claim 13 , wherein the surface treatment is galvanizing or thin layer zinking.  
   
   
       15 . The process according to  claim 1 , wherein the pre-form is a collection of multiple heat deformable steel sheets, of which at least one is comprised of a hardenable steel.  
   
   
       16 . The process according to  claim 1 , wherein the shaped part is used to produce shell parts for the hollow beams or carriers integrated in the passenger cell of a vehicle undercarriage.  
   
   
       17 . The process according to  claim 1 , wherein from the shaped part shell parts are produced for a hollow beam integrated in the undercarriage of a vehicle.